EXACT AND ASYMPTOTIC SYNTHETIC MULTIPLET SPECTRA ON AN ELLIPSOIDAL EARTH

Summary. Exact spectra of a normal mode multiplet nSl or nTl on a non‐rotating ellipsoidal earth are composed of l+ 1 lines. Asymptotically, in the limit of large l, such spectra appear, however, as a single line or peak broadened by attenuation alone. The location within the multiplet of this single peak depends only upon the angle of inclination of the source‐receiver great circle path to the axis of ellipsoidal symmetry. The appearance of a single peak is produced by the cancellation of nearby singlets. To assess the utility of the single peak approximation, exact and asymptotic synthetic spectra have been compared directly for a number of multiplets and for a variety of source‐receiver configurations. Except in the immediate vicinity of the source and its antipode, the approximation appears to be satisfactory on an ellipsoidal earth down to about l∼ 10. Additional studies will be required to determine the limits of validity on a laterally heterogeneous earth. Copyright © 1979, Wiley Blackwell. All rights reserved